Standard Science Primary 6 Energy

Siti placed a plant in a dark cupboard for two days. She then tested a leaf for starch. What is the likely result and reason?

A The leaf turns blue-black because starch is produced.
B The leaf turns blue-black because the plant made food in the dark.
C The leaf remains brown because the plant died instantly.
D The leaf remains brown because starch was used up and not replaced.
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Worked Solution

Step 1: Starch test involves iodine (brown to blue-black). Step [2-9]: In the dark, the plant cannot perform photosynthesis to make new food. Step [2-9]: The plant uses its stored starch for survival. Step [2-9]: After two days, starch is depleted, so the iodine remains brown.

Correct answer: The leaf remains brown because starch was used up and not replaced.

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